This invention relates to data storage memory systems and more particularly to improvements therein.
One of the problems which confronts manufacturers of memories of the type that have rows and columns of storage cells, is that after the memory is assembled, it is found that one or more of the storage elements are defective. It can also happen, that after the memory is in use, the one or more of the storage elements can become defective for a number of reasons, which are of no concern here. A number of different approaches are taken to overcome such defects unless the number of defective elements is so large as to require scrapping the memory. A favored technique is to use spare rows and/or spare columns of memory elements to store data which cannot be stored in regular rows or columns in memory and the entire row or column in the memory in which defective elements are present is not used.
This technique, while effective, increases the cost of the memory and can also cause a greater reduction in the storage capacity of the memory that is actually required by the number of defective storage elements.